| Aerodynamic characteristics have become crucial factors for vehicle, especially open-wheel race cars. One of the most important differences between winning and losing a race is a race car that has good aerodynamic characteristics because race car engines and body styling have advanced towards their limits in innovation and optimization or are regulated in racing. Although the study of aerodynamic characteristics have been studied and strong growth by the racing team as: Ferrari, Mc Laren, Williams, Sauber... but no study results regarding the flow field around the whole open-wheel race car has been published in the open source literature because the competition between the racing teams. Therefore, the objective of this thesis presents an investigation the aerodynamics characteristics of an open-wheel race car using experimental and computational(CFD) techniques.A 1:3 full-scale open-wheel race car was used for the experimental investigations and the geometry was built in the CFD model. The tests were conducted at a Reynolds number, based on the length of the open-wheel race car, of 3.11 x 106. Both stationary and rotating wheels cases were tested with fixed ground planes. The aerodynamic forces include of drag force and lift force are presented in this thesis. The experimental method is conducted in the HD-2 win tunnel of Hunan University. The experimental and computational methods for drag coefficient have been studied and the experimental results are good agreement with the computational results. As to the lift coefficient, experimental results are always different from computational results. Relative to the drag coefficient value, the lift coefficient value is easily affected by the uncertainties of the model installation in wind tunnel or wind tunnel structure and so on. Hence, the repeatability of the lift coefficient is bad, and the lift coefficients are quite different for the same model which is measured in different wind tunnels.In computational methods, the grid generation, turbulence model, and the method of turbulent closure, boundary condition are impact to the aerodynamic forces results, hence, these issue are also disused in this thesis. Through the experimental results, an optimum solver the Realizable k-? turbulence model was selected after comparison drag coefficient result of Realizable k-? turbulence model with the others turbulence results. It was accurately predicted that the stationary wheel generates drag coefficient good agreement with the result of experimental. In experimental method, the suction system close and open are demonstrated effect to the results of drag coefficient and lift coefficient. In case the suction system close, the drag coefficient is 0.828 and lift coefficient is-0.1105, whereas, the drag coefficient is 0.852 and lift coefficient is-0.150 in the case suction system is open at the same velocity 30m/s. The experimental techniques Particle Image Velocimetry(PIV) is used to investigate the flow-field around the open-wheel race car. The static pressure, velocity magnitude, velocity streamline are observe clearly in this thesis. The PIV velocity fields clearly show the flow structures in the surface velocity distributions on center plane of the rear wing. The influences of the rotation of the wheel on the flow field structures were investigated. Through the Figures, it can be concluded that the wake structures at the center plane of rotating wheel are more complex than the stationary wheel. The MRF method combine with the Realizable k-? turbulence model are used to investigation the rotating wheel case. The early flow separation, which is a characteristic of the rotating wheel, was observed in the surface static pressure distributions and comparison the position of separation points as well as stagnation points between the stationary wheel case and rotating wheel case. Down forces and drag forces were found to decrease as a result of rotating wheel case. The experimental results and computational results are presented graphically which helps to elucidate the aerodynamic characteristics around the open-wheel race car.The principal aerodynamic goal was to have a design that minimized drag in order to maximize top speed. As we know, the open-wheel race car is one of the kind of race car with high speed and powerful. The need for traction or adhesive friction between the wheels and road surface during high-speed on the straight line or turn a corners is become a important issue. The easiest and most effective solution to this problem came in the form of wings or airfoils. The angle of attack of airfoil is one of the main factor impacts to the aerodynamic forces on the whole open-wheel race car. However, increase the down force mean that increase the drag force and the lift force or down fore of open-wheel race car is mainly from the pressure difference between its upper surface and underbody. Therefore, this thesis also presents about CFD method combined with optimization algorithm using Isight software to optimization the angle of attack airfoil of rear wing. Approximate Kriging model is used to approximate the group 50 sample point(angle of attack) and conducted check the approximate Kriging model. It can be concluded that the Kriging model is a good approximate model in this research. The NSGA-II genetic algorithm is used to optimization through the approximate model. The optimization results of the angle of attack airfoil are achieved good aerodynamic characteristic results when comparison with the experimental result. The result makes maximize down force while the drag is minimizing. It is can be one of a reference for the angle of attack design of race car rear wing.In a road racing, the open-wheel race car not only moves on the straight line but also on the corners. When the race car in corner, the distribution of pressure and velocity around the open-wheel race car constantly changing. Understanding the aerodynamic characteristics of open-wheel race car in turn a corner will have the car archive the highest speed and stability. That will have greater advantages for team race in the competition. Therefore, in this thesis, author also presents the aerodynamic characteristics of open-wheel race car in turn a corner through the Fluent software combine with the User-Defined Functions(UDF). The change of aerodynamic characteristics distribution around the open-wheel race car in turn a corner is investigated through the change of time. The simulation results are display visualization graphic.Recommendations on the future work on aerodynamic characteristic around the open-wheel race car are proposed at the end of this thesis... |
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